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Re: [TCML] mmc cap protection by spark-gaps-any ideas?
Speaking of using the wrong bleeder resistors, read the story about Jeff and what happened to him when he used the wrong value resistors across the power supply caps in his 833C Tesla Coil at: http://www.audiotesla.org/Jeff%20833C%20Coil.htm (The resistors actually ran good for about 6 months before one of them flashed over and blew-up with a very loud bang during our Teslathon!)
Regards,
Woo
> [Original Message]
> From: CONOR WHYTE <cjwhyte@xxxxxxx>
> To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
> Date: 8/19/2008 10:49:15 PM
> Subject: Re: [TCML] mmc cap protection by spark-gaps-any ideas?
>
> Sorry I should have been clearer. I was tired (2am)
> I used some "bulk" resistors that were available at the time and they were NOT that cheap. (added expenses gas charge and 14.5% tax.) Yes I did notice a drop in output, maybe 4-6 inches. (maybe it was the resistors? I don't know but according to the formula I must have had very bad or poorly labeled resistors.) I never went back to using them. After I got rid of the resistors I noticed a little increase. ---
> I hope that makes a little bit more sense now ?
>
> I agree, Matt it is ideal to have the added safety. Again if I need to make any changes between firings I discharge the capacitors manually.
>
> Again sorry for the confusion.
>
>
> ----- Original Message -----
> From: mddeming@xxxxxxx
> Date: Tuesday, August 19, 2008 12:42 pm
> Subject: Re: [TCML] mmc cap protection by spark-gaps-any ideas?
> To: tesla@xxxxxxxxxx
>
> > Oops,
> > I dropped a term, Sorry.
> > P=E^2/R=12,000x12,000/200,000,000=144/200=720mw/string,
> > or 1.44W out of 2.88KW, or 0.05%. Sorry for the carelessness,
> > but it
> > still makes the claim of waste seem pretty farcical.
> >
> > Matt D.
> >
> > -----Original Message-----
> > From: mddeming@xxxxxxx
> > To: tesla@xxxxxxxxxx
> > Sent: Mon, 18 Aug 2008 4:42 pm
> > Subject: Re: [TCML] mmc cap protection by spark-gaps-any ideas?
> >
> >
> > Hi Connor,
> >
> > Congratulations on not zapping yourself, YET.
> > With resistors running about 1-2 cents each in bulk, I can't see
> > that
> > it is a major expense for added safety.
> > Many older coilers (30-yr experience+) believe they got to be
> > that way
> > by using both a J-stick AND discharge resistors.
> > Using 20 10-meg resistors would "waste" three MILLIWATTS per string.
> > I find it hard to believe that you could really notice a loss of
> > 0.006
> > watts out of 2880 watts total.
> > That's about 0.0002%! Seems like a very small price to pay for
> > the
> > added safety.
> >
> > Matt D.
> >
> > -----Original Message-----
> > From: CONOR WHYTE <cjwhyte@xxxxxxx>
> > To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
> > Sent: Sun, 17 Aug 2008 11:37 pm
> > Subject: Re: [TCML] mmc cap protection by spark-gaps-any ideas?
> >
> >
> > I don't use resistors on my MMC. I find these waste energy and
> > cut down
> > on my
> > spark length. I use CDE 942C series 1.6Kvdc 680nF capacitors, I
> > use 20
> > per
> > string 34nF @ 32Kvdc
> > x2 . I run 12Kvac @ 240mA. I have been running my
> > MMC now
> > for 2 years and have had 0 problems.
> > Quite often many people are scared about residual charge in the
> > cap
> > bank this is
> > why people add the resistors. It bleeds charge away after the
> > unit is
> > turned
> > off. You can do this with a discharge wand MUCH cheaper.
> > Like I said I have never used them. It is a waste of energy.
> > If you feel like you want to protect your cap bank, I'd might
> > make an
> > extra gap
> > that one could adjust.
> > maybe say to be safe a 3.5cm gap 35Kv. I would also make sure
> > the MMC
> > total DC
> > rating is around 3x that of the input voltage. 12Kvac -- 32-
> > 36Kvdc.
> > Another
> > factor I would also check is the tolerance rating of the
> > capacitors
> > most are
> > 5%... which is ok... CDEs on the other hand are 10% and can
> > handle much
> > more
> > voltage spikes.
> >
> >
> > ----- Original Message -----
> > From: vatercox@xxxxxxx
> > Date: Monday, August 18, 2008 10:47 am
> > Subject: [TCML] mmc cap protection by spark-gaps-any ideas?
> > To: tesla@xxxxxxxxxx
> >
> > > Dear List
> > > I have 30 x 47nF polypropylene metal foil caps, each rated at 2
> > > kVDC
> > > which I intend to wire as three strings of 10 capacitors for
> > > approximately 14nF at 20kV DC. While normally each capacitor in
> > > an MMC
> > > would be protected by a 10- or m
> > ore megohm high voltage resistor
> > > these
> > > have proved difficult to obtain (due to lack of demand?). In liu
> > > of
> > > this would it be possible to protect each cap with a miniature
> > > spark-gap -perhaps a pair of closely-positioned stiff wires
> > > connected
> > > to the capacitor leads notwithstanding the fact that 2 kV is
> > > usually
> > > regarded as a bit on the low side for satisfactory spark-gap
> > operation
> > >
> > > Jolyon Francis Vater-Cox
> > >
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